targetcli /backstores/fileio create fails for LVM devices with uppercase names

Issue

• Attempting to create a new fileio device through targetcli against an LVM device fails.
• The error message (for an LVM volume named 'somelvname' with some or all letters in upper case) is:

IOError: [Errno 2] No such file or directory: '/sys/block/somelvmname/size'

• In more detail, here is the full python traceback for an LVM volume named TESTVG-testlv :

[root@rhel70 ~]# lvs
  LV     VG     Attr       LSize   Pool Origin Data%  Move Log Cpy%Sync Convert
  testlv TESTVG -wi-ao----   8.00g                                             
  root   rhel   -wi-ao----  13.71g                                             
  swap   rhel   -wi-ao---- 820.00m                                             

[root@rhel70 ~]# targetcli /backstores/fileio create test /dev/mapper/TESTVG-testlv 
Note: block backstore preferred for best results
Traceback (most recent call last):
  File "/usr/bin/targetcli", line 89, in <module>
    main()
  File "/usr/bin/targetcli", line 72, in main
    shell.run_cmdline(" ".join(sys.argv[1:]))
  File "/usr/lib/python2.7/site-packages/configshell/shell.py", line 891, in run_cmdline
    self._execute_command(path, command, pparams, kparams)
  File "/usr/lib/python2.7/site-packages/configshell/shell.py", line 866, in _execute_command
    result = target.execute_command(command, pparams, kparams)
  File "/usr/lib/python2.7/site-packages/targetcli/ui_node.py", line 87, in execute_command
    pparams, kparams)
  File "/usr/lib/python2.7/site-packages/configshell/node.py", line 1417, in execute_command
    result = method(*pparams, **kparams)
  File "/usr/lib/python2.7/site-packages/targetcli/ui_backstore.py", line 355, in ui_command_create
    % (name, so.size))
  File "/usr/lib/python2.7/site-packages/rtslib/tcm.py", line 611, in _get_size
    return (get_blockdev_size(self._parse_info('File')) *
  File "/usr/lib/python2.7/site-packages/rtslib/utils.py", line 127, in get_blockdev_size
    return get_size("/sys/block/%s" % name)
  File "/usr/lib/python2.7/site-packages/rtslib/utils.py", line 120, in get_size
    sect_size = int(fread("%s/size" % path))
  File "/usr/lib/python2.7/site-packages/rtslib/utils.py", line 88, in fread
    with open(path, 'r') as file_fd:
IOError: [Errno 2] No such file or directory: '/sys/block/testvg-testlv/size'